Diffusion model for selective area growth of cubic GaN under MOVPE process

Abstract

Diffusion models were applied in order to describe the thickness profiles and morphologies of cubic GaN grown by selective area growth under metalorganic vapor phase epitaxy with narrow open windows. The simulated results from vapor phase diffusion model with D/k - the ratio of diffusion coefficient to the deposition rate constant – of 15 μm was found to agree well with the film thickness profile for fill factor higher than 0.5, while for fill factor lower than 0.5 the predicted values were found to be lower than the experiments. Moreover, the abnormal growth rate occurring at the edge connecting (111)B sidewall facets and (001) plane could not be explained by the simulation results. The inconsistency was believed to result from the lack of the effects from surface migration process. Therefore the results from surface migration model were added to the previous results, and the improvement of the thickness profiles between the simulation and experiment was observed. The experimental profiles with fill factor lower than 0.5 was found to be well fitted with the simulation results with surface migration length and the weight of surface migration contribution of 0.8 μm and 0.03 min[superscript -1], respectively. Also, the simulation results were able to describe the abnormal growth rate at the edges and consequently suggest a way to reduce hexagonal inclusion which has been observed in c-GaN.